Patent GB-191420664-A (GB)
Title: Improvements in Machines for Making Twist Drills, and other Similarly Grooved Metal Articles.
Inventor: JUSTICE PHILIP MIDDLETON
IPC: B23C3/32
Filed: 1914-10-07
Granted: 1915-08-12
Abstract: 2 0 , 6 6 4. Justice, P. M., [Pratt & Whitney Co.]. Oct. 7. Milling helical surfaces; turning; chucks. -A machine for manufacturing twist drills from bar stock has the stock intermittently fed through a hollow spindle carried by a slide which produces the feed for cutting the grooves. Two cutters are employed, one cutting a groove and the other relieving a land. Two traverses of the slide complete a drill, .the work being indexed during the idle return. The cutters have motions for withdrawing them from the cut, and for giving the customary variation i n thickness of the core while preserving a constant width of flute. The spindle 3, Fig. 23, is fitted with a push spindle chuck 9 operated by a cone 18 and levers 21, Fig. 1, from a cam drum 27 geared to the cam shaft 14, driven from the main shaft 42 through a twospeed gear controlled by a clutch operated by a dog-wheel 54. The stock is fed by a pair of sleeves 8, 8<1> also controlled by the cam drum. The sleeve 8 has a flared end and the sleeve 8<1> pockets for retaining a number of balls. Relative movement of the sleeves causes the balls to grip and release the stock as required. When the stock is exhausted a spring 11<1>, Fig. 23, causes the sleeves to assume the relative position shown in Fig. 25, the flange 12<1> then being removed from the lever 221. The spring 227 rocks the shaft and brings the finger 232 into such position that at the close of the return movement of the spindle slide 5 a ring is pushed off a pin. The ring is connected to belt striking gear and the release from the pin allows a spring to throw the forks and stop the machine. The slide 5 is fed by a camdrum 32 acting through a reversely moving slide 34 and rack-and-pinion gearing. A rack 58 carried bv the slide 34 is connected through change-gearing with a wheel 62 loose on the spindle. A ratchet and a lost-motion device. Fig 13, are employed and the whole gearing is so adjusted that the correct lead is generated on the forward stroke while during the return indexing through half a revolution occurs. To avoid slip a roller ratchet in one of the bearings prevents reverse rotation of the spindle 3. The slide 34 carries three relatively adjustable formers which control the movements of the cutter slides. A saddle 81, Fig. 4, is guided on the bed by a central rib 82, and gibs 83. A slide 84, carrying the grooving - cutter 90 through an intermediate slide 87 movable parallel to the axis of the cutter, is controlled by a lever 106, engaging one of the formers. and by a spring 104. The initial thickness of the core is controlled by a screw 107. A lever 127 similarly controls the slide 114 carrying the relieving-cutter. When the required length of flute has been cut, rapid rises on the formers remove the cutters clear of the work. A detent engaging the levers 106, 127 retains the slides in this position during the return of the slide 5, but is tripped by a stop on the slide 34 at the close of such movement. In order that the withdrawal of the cutter 90 during the thickening of the core may not decrease the width of groove cut, a rod 138, Fig. 6, continuously reciprocated by a lever 152 operated by a cam geared to the shaft 42, tends to reciprocate a block 136 secured to the cutter slide 87 through springs 143. The extent of movement permitted is varied from nothing to a maximum by means of the third former which is connected to rock a lever having pins 149<1> situated on either side of the block 136. Axial movement of the cutter spindle in its slide is prevented by collars 94, Fig. 4. The pinions 98, 99 of the cutter drive are wide enough to permit of the reciprocations of the slide 87, the drive being through screw gearing from the shaft 42. In a modification, the width of groove is preserved by oscillating the cutter angularly through the construction shown in Fig. 22. After the second flute has been cut, a cam 41 holds the slide 5 with a dwell in its forward position and a cam 202 actuates a lever system to close a clutch 188, thereby rotating a head 170 concentric with the spindle. Other connexions acting through a sliding sleeve rock an arm 172, Fig 9, to effect the cutting-off of the finished drill.